Vortex cleaner

Abstract

A vortex cleaner for separating fibrous suspensions into fractions, in particular for cleaning papermaking pulp suspensions from impurities as chips, shives, sand grains, metal particles, etc., comprises an elongate vortex chamber, which has a circular cross-section and which over part of its length tapers towards its one axial end. The larger end of this vortex chamber has at least one tangential inlet for the suspension to be treated and an axial accept outlet for a lighter fraction of the treated suspension. The smaller end of the vortex chamber has an axial reject outlet for a heavier fraction of the treated suspension. The tapering part of the vortex chamber has a boundary wall which consists of one or preferably two ledges, which face the larger end of the vortex chamber and extend helically with diminishing diameter towards the smaller end of the vortex chamber, and a sidewall interconnecting the consecutive convolutions of said ledge or ledges. This sidewall is inclined relative to the axis of the vortex chamber so as to be conically divergent towards the smaller end of the vortex chamber.

I claim: 
     
       1. A vortex cleaner for separating a fibre-liquid-suspension, in particular an aqueous suspension of papermaking pulp, into fractions, comprising an elongate vortex chamber, which has a circular cross-section and which over part of its length tapers towards one axial end of the chamber, said chamber having at its larger end a substantially tangential inlet for the suspension to be treated and a first, axial outlet for a lighter fraction of the treated suspension and at its smaller end a second, axial outlet for a heavier fraction of the treated suspension, the boundary wall surrounding said tapering part of the vortex chamber having at least one ledge, which faces the larger end of the vortex chamber and extends helically with a diminishing diameter towards the smaller end of the vortex chamber with a direction of rotation about the axis of the vortex chamber corresponding to the flow direction of a suspension flow injected through said tangential inlet, and a sidewall interconnecting the consecutive convolutions of said ledge, said sidewall being inclined relative to the axis of the vortex chamber so as to be conically divergent towards the smaller end of the chamber. 
     
     
       2. A vortex cleaner as claimed in claim 1, wherein the angle of inclination of said sidewall relative to the axis of the vortex chamber lies within the range up to 5° 
     
     
       3. A vortex cleaner as claimed in claim 2, wherein said angle of inclination lies within the range from 1° to 4°. 
     
     
       4. A vortex cleaner as claimed in claim 1, wherein the pitch of said helically extending ledge is of the same magnitude as the axial dimension of the entrance opening of said tangential inlet to the vortex chamber. 
     
     
       5. A vortex cleaner as claimed in claim 1, wherein said ledge is substantially perpendicular to the axis of the vortex chamber, as seen in an axial section. 
     
     
       6. A vortex cleaner as claimed in claim 1, wherein said ledge is somewhat inclined towards the smaller end of the vortex chamber, as seen in an axial section. 
     
     
       7. A vortex cleaner as claimed in claim 1, wherein said ledge has a substantially constant width over its entire length. 
     
     
       8. A vortex cleaner as claimed in claim 1, wherein the boundary wall surrounding the tapering part of the vortex chamber at least two helically extending ledges of the kind defined, said ledges being disposed relative to each other in a manner similar to the thread grooves of a screw-thread with several entries.